- Remove the `--evm` option on non-EVMC builds.
`when` around an option doesn't work with confutils; it fails to compile.
Workaround that by setting the `ignore` pragma on EVMC-specific options.
(Thanks @jangko for that new pragma). I prefer this to a solution which
moves the whole option's pragma elsewhere, especially if we add more options.
- Improve the help text, so that it shows the standard library extension on
each target platform (or none if on another platform).
- Undo b3f21bf4 "add missing evmc_enabled conditional compilation in
evmc_dynamic_loader". Move the conditional to `nimbus.nim`, and take more
care there to only use the loader function in EVMC builds.
It's ok to just not include this EVMC-only module (like some other EVMC
modules), rather than making the module itself a bit broken: Without this
change, it references a function that's not imported or linked to, and it
only links because there is no call sequence reaching that function.
Signed-off-by: Jamie Lokier <jamie@shareable.org>